Explosive



Patented Dec. 16, 1941 EXPLOSIVE.

Don Chester Lindsten, Penns Grove, N. J., as- Signor to E. I. du Pont de Ne'mdurs accompany, Wilmington, DeL, a corporation of Delaware No Drawing. Application February 6, 194 5,

Serial No. 576,504

1 Claim. (Cl.

This invention relates to a novel and improved propellent powder and more particularly to one having superior ballistic properties.

In formulating powders for use in small arms, it is desirable to control the ballistic properties so that combustion will be uniform and progressive and so that unduly high temperatures and pressures will not be attained within the gun barrel. In order to promote progressive burningfit has been the practice to apply coatings of deterrent materials to the surface of the smokeless powder grains. This has been done in the case of both single base anddouble base powders and has been particularly desirable with the latter type because of the high potential of propellants containing nitroglycerin.

Several types of deterrent have been used in the past, all of which suffer important disadvam tages, especially when applied to nitroglycerin powders. Centralite, for example, introduces manufacturing hazards because it must be applied at temperatures of 70 C. or above. Dinitror lu n e ds topenetrate com l t y throu h the po d n. nd hus to de t oy e pr ssiv b nin p o rt o h owde An b e th p esent vent s a. p pellent smokeless powder, of improved ballistic properties. A further object is such a powder composition having burning characteristics that give the powder outstanding superiority. A still further-object is a smokeless powder having its grains surface-coated with a new type of deterrent material, and a method of applying such coating. Additional obiects will be disclosed as the invention is described more fully in the following.

I have found that the foregoing advantages are accomplished when I repare smokeless powder grains and impart to them a coating of a substantially water-insoluble ester of a dicarboxylic aliphatic acid, desirably one'having a melting point below 100 C. While varying amounts of such ester may be used and will provide an effective deterrent coating to the powder, I prefer to maintain an amount of the ester on the grains amountingto between 0.2% and 10.0% of the total weight of powder. Moreover, the coating material may be applied to any type of propellent smokeless powder, whether to single base powders, where nitrocellulose is the only nitric ester, or to double base powders, in which nitroglycerin or other high explosive nitric ester is present with the nitrocellulose. It may well be used also for cellular type powders, either single .or double base, where a cellular structure has been oxylic aliphatic acids. Nonvolatility is desirable,.

as it means that there will be substanti'ally no loss of coating material during manufacture and storage, hence no change in ballistic properties for such reason. Water-insoluble coatings are desirable, as they favor decreased hygroscopicity ofproduct. As examples of esters suitable for use, we may cite dibutyl tartrate; the tartaric acid di-ester of ethylene glycol monobutyl ether better known as di(butylcellosolve) tartrate; the sebacic acid di-ester of ethylene glycol monobutyl ether known as di(butylcellosolve) sebacate; di'b-utyl adipate; the adipic acid di-ester of ethylene glycol monoethyl ether known as di'cellosolve adipate; fumaric acid esters; and many others. Certain mixtures of lower esters ordicarboxylic acids higher than adipic have likewise been found advantageous. Desirably the coating "agent will possess a certain degree ofsolubility for nitrocellulose, but this'is not essential.

Various methods maybe employed in coating the powder grains. Qne applicablemethod consists n. p eparin w te s u r e con a n the powder and suspended ester, Preferably, how ever, T agitate the powder with about an equal weight of water in a tumbling and mixing device such as a sweetie barrel and spray the coating agent in liquefied form onto the powder surfaces. In order to obtain uniform distribution at temperatures which are not too high for safety, I prefer to use a coating agent that is liquid at temperatures of 20 C. or lower, and in any case one that has a melting point below C. If desired, the spraying operation may be facilitated by diluting the deterrent with a volatile liquid of low viscosity, such as ethyl alcohol.

The following examples will serve to illustrate specific embodiments of methods of carrying out the invention, but are not to be taken as limiting it in any way.

Example 1 A smokeless powder colloid containing 16% finely divided potassium nitrate was pressed, and cut into grains of diameter 0.050 in. and length V12 in. The potassium nitrate was then extracted in water and the powder impregnated with 15% nitroglycerin, Part A of the powder was finished in the usual manner comprising the operations 9i air dryin glazing, and sieving.

Part B was introduced into parts of water at room temperature and agitated for 2 hrs. During the first 1 hrs., 4%, on the weight of the powder, of dibutyl adipate was added dropwise to the slurry. At the end of the coating treatment the powder was air dried, glazed and sieved in the usual manner.

The samples were then fired in a caliber .22 gun, using long rifle components, and 40-gr.

lead bullets, with the following results:

Charge, Velocity Pressure, Part Powder Coatmg grains ItJsec. lb./sq. in.

A None 1. 82 1, 323 27, 510 B Dibutyl adipate 2. 50 l, 326 23, 510

These ballistics show the value of the coatin agent in that a very appreciable decrease in pressure was obtained with a slightly increased velocity.

Example 2 A powder similar to that of Example 1, but pressed and cut to a diameter of 0.041 in. and a length of in., was treated as follows:

Part A was finished by air drying, glazing with graphite and calcium stearate, and sieving.

Part B was introduced into a sweetie barrel with water. The wet powder was then tumbled for 25 min. while a 50-50 solution of di(butylcellosolve) tartrate and ethyl alcohol was sprayed onto the powder at room temperature. The di(buty1cellosolve) tartrate was used in the amount of 2.75% of the dry powder weight. After the addition of the coating agent, the powder was tumbled an additional hour. It was then removed from the barrel and finished in the same manner as part A.

The powders showed the following ballistics in Again a very marked improvement in ballistics was obtained by use of the coating agent, The coated powder had a much higher velocity aFa lower pressure,

The foregoing examples have illustrated the invention by reference to propellants containing nitroglycerin, but it will be apparent that advantages will be obtained equally with single base powders. The water-insoluble ester applied will be mainly on the surface of the treated powder but will, of course, penetrate the wet powder slightly. The material applied will, however, be definitely present as a coating and not as a blended ingredient.

The advantages of the invention are apparent in that it allows the preparation of a propellent smokeless powder of superior ballistic properties. Since the coating materials are in liquid form at moderate temperatures of application, the necessity, is avoided of heating the powder to elevated temperatures during the treatment. This avoids all safety hazards from elevated temperature treatment, as well as loss of nitroglycerin, when double-base powders are coated, by volatilization or solubility in excessively hot water.

While the invention has been described in full in the foregoing, it will be apparent that many variations in details of compositions and procedures may be introduced without departing from the scope of the invention. I intend to be limited, therefore, only by the following claim.

I claim:

A propellent powder composition comprising smokeless powder grains having a surface coating of di(butylcellosolve) tartrate, said coating being present in-an amount between 0.2 and 10.0% of the total weight of the powder.

DON CHESTER LINDSTEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,198,746 Spurlin Apr. 30, 1940 2,179,312 Allison Nov. 7, 1939 2,118,506 Graves May 24, 1938 2,186,516 Boddicker Jan. 9, 1940 2,076,772 Goodyear Apr. 13, 1937 FOREIGN PATENTS Number Country Date 356,256 Great Britain Sept. 7, 1931 27,197 Great Britain A. D. 1896 

